Automatic sprinkler heads, as used in commercial and industrial buidings, include a cast metal frame having a base that defines an outlet connected to the water piping system. The frame also includes a pair of arms that extend outwardly from the base and are connected together at a junction. The outlet in the base is normally enclosed by a cap, which is held in the closed position by a lever assembly, that extends between the cap and the junction. The lever assembly includes a pair of lever members, with one of the lever members being normally biased in a direction away from the other.
In the conventional sprinkler head, a fusible link, including a fusible element or metal, retains the lever assembly in position to close off the outlet. On exposur to an elevated temperature, the fusible metal will melt, releasing the link and the lever assembly to open the outlet to the water line.
The primary use in the past of automatic sprinkler systems has been for property protection in commercial and industrial applications, such as warehouses, stores, buildings and the like. With the recent increased use of sprinkler systems in hospitals, hotels, nursing homes and residences, where the prime object is to save human life as opposed to property protection, there is a demand for a faster response sprinkler head, meaning one that will release more quickly when exposed to elevated temperatures.
U.S. Pat. No. 4,273,195, discloses a fast response sprinkler head, in which the fusible link that retains the lever assembly in the engaged position includes a pair of their copper sheets connected by a layer of solder. Each sheet has an opening to receive one of the lever members. The major portion of the fusible link of the aforementioned patent is located between the lever members in a location where the lever members tend to shield the central portion of the link. Because of this, a side edge of each sheet is formed with an angular wing which is disposed at an acute angle to the sheet and is designed to direct heated air onto the central portion of the fusible link.